My tank has been set up and cycling for 9 days now and I've been testing the water every day (liquid test kit)
There's a definate bacterial bloom going on because the water has suddenly gone very cloudy.

Tonight, the ammonia level is 0.25. Nitrite is still 0

But I'm confused at why the nitrate has suddenly shot up to 10 (it was 5 yesterday). Isn't the nitrite supposed to rise first?

Tank volume: 400 litres approx
Filter: Fluval FX5
Tank contents: 6 zebra danios
Water temp: 27 deg celcius

Have you tested your tap water? Are you using any other chemicals to cycle the tank?

The tap water nitrate reading is 5.0

The only other chemical I've added to the water is "King British Water Conditioner". (Does exactly the same as Prime) That was added when I first filled the tank.

You're right, ammonia comes first, then nitrites, and finally nitrates.
Maybe the conditioner has something to do with that?
Just keep testing in the coming days, and see what happens.

i wouldnt worry about the nitrate rising a little. Are you sure its not your reading of the chart. The best time to test is during the day and look at the chart in bright sunlight otherwise you can get an incorrect reading (this applies more to differentiating the shades of red)

Keep testing and you will see the cycle start soon.

Funnily enough I tested the tap water for nitrates the other morning and I could see the colour much clearer than the evening. The tap water is 10, not 5!

I've got another problem however..

I've had to put Munch, my 10in pleco in the tank prematurely. He was temporarily housed with my goldfish until this tank is safe. I've had to move him into his home early because he was shredding my fancy goldfish's fins to shreds as he ploughed his way past them

Am I screwing up the tank cycling process as I'm having to do water changes now?
Is Munch safe??

Water readings this morning:
Ammonia: 0.25
Nitrite: 0
Nitrate: 10
pH: 7.8

(Munch is still very alert and eating well.. as well as ignoring his tunnel, he prefers to bury himself in the sand right next to it )

You wont screw up the cycling process by adding the plec. The plec will prosuce ammonia like the danios

However, it will take longer to cycle your filter as you will have to do water changes to keep the ammonia and nitrite down, i would do daily 25% water changes. If you dont do this then you risk your plec getting ill or dieing